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FLUIDS AND ELECTROLYTES
Amjad Bani Hani Ass.Prof. of Cardiac Surgery & Intensive Care
Body Water Content
Water Balance: Normal
0
500
1000
1500
2000
2500
Output Intake
Metab
Food
Fluids
Stool
Breath
Sweat
Urine
Water Output: Normal vs.Exercise
0
1000
2000
3000
4000
5000
Normal Exercise
Stool
Breath
Sweat
Urine
Water Intake: Normal vs Exercise
0
1000
2000
3000
4000
5000
Normal Exercise
Metab
Food
Fluids
Electrolytes
Electrolytes
Solutes that form ions (electrical charge)
Cation (+)
Anion (-)
Major body electrolytes:
Na+, K+, Ca++, Mg++
Cl-, HCO3-, HPO4--, SO4-
Electrolyte Distribution
Major ICF ions
K+
HPO4--
Major ECF ions
Na+
CL-, HCO3-
Intravascular (IVF) vs Interstitial (ISF)
Similar electrolytes, but IVF has proteins
Mechanisms Controlling Fluid and Electrolyte Movement
Diffusion
Selective Permeability
Facilitated diffusion
Active transport
Osmosis
2*Na + BUN + Glucose/18
Hydrostatic pressure
Oncotic pressure
Cells are selectively permeable
Sodium is the largest Determinant of Osmolality
Na+: 135 – 145 mEq/L
Ca+: 8.5 – 10.5 mEq/L
K+: 3.5 – 5 mEq/L
Osmolality~ 2*(Na+) = 2*(135 - 145 mEq/L) Normal (Isotonic) 280 – 300
Low (hypotonic) < 280
High (hypertonic) > 300
Fluid Exchange Between Capillary and Tissue: Sum of Pressures
Fig. 17-8
Fluid compartments
ICF
ECF
Interstitial
Fluid compartments
ICF
ECF
Interstitial
Fluid compartments
ICF
ECF
Interstitial
Capillary Membrane
Fluid compartments
ICF
ECF
Interstitial
Capillary Membrane
Fluid compartments
ICF
ECF
Interstitial
Capillary Membrane Cell Membrane
Colloid osmotic pressure
ECF
Interstitial
Capillary Membrane
Capillary membrane freely permeable to water and electrolytes but not to large molecules such as proteins (albumin).
Colloid osmotic pressure
ECF
Interstitial
Capillary Membrane
Capillary membrane freely permeable to water and electrolytes but not to large molecules such as proteins (albumin).
Colloid osmotic pressure
ECF
Interstitial
Capillary Membrane
Capillary membrane freely permeable to water and electrolytes but not to large molecules such as proteins (albumin).
The albumin on the plasma side gives rise to a colloid osmotic pressure gradient
favouring movement of water into the plasma
H2O
H2O
Colloid osmotic pressure
ECF
Interstitial
Capillary Membrane
Capillary membrane freely permeable to water and electrolytes but not to large molecules such as proteins (albumin).
The albumin on the plasma side gives rise to a colloid osmotic pressure gradient
favouring movement of water into the plasma
This is balanced out by the hydrostatic pressure difference
H2O
H2O 120/80
H2O
H2O
Cell Membrane
ICF
Cell Membrane
Interstitial
H2O
H2O
Cell membrane is freely permeable to H20 but
Cell Membrane
ICF
Cell Membrane
Na+
K+
Interstitial
H2O
H2O
Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!
Cell Membrane
ICF
Cell Membrane
Na-
K+
Interstitial
H2O
H2O
Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!
[K+] =4
Cell Membrane
ICF
Cell Membrane
Na-
K+
Interstitial
H2O
H2O
Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!
[K+] =4 [K+] =150
Cell Membrane
ICF
Cell Membrane
Na-
K+
Interstitial
H2O
H2O
Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!
[K+] =4 [K+] =150
Na+= 144
Cell Membrane
ICF
Cell Membrane
Na-
K+
Interstitial
H2O
H2O
Cell membrane is freely permeable to H20 but Na and K are pumped across this membrane to maintain a gradient!
[K+] =4 [K+] =150
Na+= 144 Na+= 10
Hypernatremia
Manifestations Thirst, lethargy, agitation, seizures, and coma
Impaired LOC
Produced by clinical states Central or nephrogenic diabetes insipidus
Reduce levels gradually to avoid cerebral edema
Hyponatremia
Results from loss of sodium-containing fluids
Sweat, diarrhea, emesis, etc.
Or from water excess
Inefficient kidneys
Drowning, excessive intake
Manifestations
Confusion, nausea, vomiting, seizures, and coma
Hyperkalemia
High serum potassium caused by
Massive intake
Impaired renal excretion
Shift from ICF to ECF (acidosis)
Drugs
Common in massive cell destruction
Burn, crush injury, or tumor lysis
False High: hemolysis of sample
Hyperkalemia
Manifestations
Weak or paralyzed skeletal muscles
Ventricular fibrillation or cardiac standstill
Abdominal cramping or diarrhea
Hypokalemia
Low serum potassium caused by
Abnormal losses of K+ via the kidneys or gastrointestinal tract
Magnesium deficiency
Metabolic alkalosis
Hypokalemia
Manifestations
Most serious are cardiac
Skeletal muscle weakness
Weakness of respiratory muscles
Decreased gastrointestinal motility
Calcium
Obtained from ingested foods
More than 99% combined with phosphorus and concentrated in skeletal system
Inverse relationship with phosphorus
Otherwise…
Calcium
Bones are readily available store
Blocks sodium transport and stabilizes cell membrane
Ionized form is biologically active
Bound to albumin in blood
Bound to phosphate in bone/teeth
Calcified deposits
Calcium
Functions
Transmission of nerve impulses
Myocardial contractions
Blood clotting
Formation of teeth and bone
Muscle contractions
Calcium
Balance controlled by
Parathyroid hormone
Calcitonin
Vitamin D/Intake
Bone used as reservoir
Hypercalcemia
High serum calcium levels caused by
Hyperparathyroidism (two thirds of cases)
Malignancy (parathyroid tumor)
Vitamin D overdose
Prolonged immobilization
Hypercalcemia
Manifestations
Decreased memory
Confusion
Disorientation
Fatigue
Constipation
Hypocalcemia
Low serum Ca levels caused by
Decreased production of PTH
Acute pancreatitis
Multiple blood transfusions
Alkalosis
Decreased intake
Hypocalcemia
Manifestations
Weakness/Tetany
Positive Trousseau’s or Chvostek’s sign
Laryngeal stridor
Dysphagia
Tingling around the mouth or in the extremities
IV Fluids
Purposes 1. Maintenance
When oral intake is not adequate
2. Replacement
When losses have occurred
Kinds of IV Fluid solutions
Hypotonic - 1/2NS
Isotonic - NS, LR, albumen
Hypertonic – Hypertonic saline.
Crystalloid
Colloid
IV Fluids
Crystalloids
Colloids
PRBCs
Albumin
Dextran
FFP
D5W
Hypotonic
Hypertonic
Isotonic
½ NS ½ NS (0.45%)
Lactated Ringer
NS (0.9%)
Plasmalyte
D5W in ½ NS
D10W
3% Saline
D5W (Dextrose = Glucose)
Hypotonic
Provides 170 cal/L
Free water Moves into ICF
Increases renal solute excretion
Used to replace water losses and treat hyponatremia
Does not provide electrolytes
Normal Saline (NS)
Isotonic
No calories
More NaCl than ECF
30% stays in IVF
70% moves out of IV space
Normal Saline (NS)
Expands IV volume
Preferred fluid for immediate response
Risk for fluid overload higher
Does not change ICF volume
Blood products
Compatible with most medications
Lactated Ringer’s
Isotonic
More similar to plasma than NS
Has less NaCl
Has K, Ca, PO43 , lactate (metabolized to
HCO3 (
CONTRAINDICATED in lactic acidosis
Expands ECF
Plasma Expanders
Stay in vascular space and increase osmotic pressure
Colloids (protein solutions)
Packed RBCs
Albumin
Plasma
Dextran
THANK YOU
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